This invention relates generally to electrical switches and more particularly to switches using snap acting disc elements which move between opposite convex and concave configurations and which are actuated upon the occurrence of selected conditions such as pressure or temperature.
Conventional condition responsive switches have a contact arm movable between first and second switch positions prebiased to one switch position and have a dished snap acting disc element movable between opposite convex and concave configurations for moving the switch between switch positions in responsive to the occurrence of selected temperature or pressure conditions. Such switches are intended to perform selected control functions in response to the occurrence of the selected temperature or pressure in a zone to be monitored.
In automobiles there are a number of different applications requiring such switches however the specific conditions vary significantly in some cases thereby requiring different switch characteristics. In certain applications, such as when monitoring compressor pressures a reliable seal which will prevent loss of freon for an indefinite period of time is important as well as having a switch which will perform the selected control function as intended. In certain applications the outside dimensional characteristics of the housing is critical. That is when received in a compressor well, the outer dimensions of the switch after final assembly must be very closely controlled with no bulging of the housing due to assembly techniques being permitted. Even the switch components need to be changed to some extent in order to meet various switching requirements. That is, when it is intended to monitor high pressures, a pressure converter may be required to convert pressure exposed to a diaphragm to a selected force level applied to the snap acting disc. In other applications in which a lower pressure is monitored the pressure converter is not always required. Another characteristic which can vary from one application to another is whether the disc is used to provide contact closure force or contact open force.
While the many requirements noted above can be met by conventional switches their use is limited by various factors such as undesirable variations in thermal or pressure response characteristics due to problems with seating of the disc or limiting overtravel of the disc without causing deleterious effects on the disc calibration. Other limitations include inconsistent and unreliable seals for pressure responsive switches and high costs due, inter alia, to low volume production in order to serve segmented functional needs.